Most inherited cases of breast cancer are associated with one of two abnormal genes: BRCA1 (BReast CAncer gene one) or BRCA2 (BReast CAncer gene two).

Women with a BRCA1 or BRCA2 genetic mutation:

have up to a 72% lifetime risk of developing breast cancer

have a much higher-than-average lifetime risk of ovarian cancer; estimates range from 17% to 44%

U.S. guidelines say that BRCA testing should be considered when:

many women in a family have been diagnosed with breast and/or ovarian cancer, particularly if the women were younger than 50 when diagnosed

some women in a family have been diagnosed with cancer in both breasts

there is both breast and ovarian cancer in a family

men in a family have been diagnosed with breast cancer

there is breast cancer in a family and either male relatives on the same side of the family have been diagnosed with prostate cancer at a young age or relatives on the same side of the family have been diagnosed with gastrointestinal cancers, such as pancreas, gall bladder, or stomach cancer

a family is of Ashkenazi (Eastern European) Jewish descent

To do the study the researchers sent a survey on genetic testing to 2,529 women who had been diagnosed with stage 0 to stage II breast cancer between July 2013 and September 2014. The women were between 20 and 79 years old and lived in Georgia and Los Angeles, Calif.

The characteristics of the women in the study:

56.8% were white

17.8% were black

13.9% were Hispanic

8.9% were Asian

half were older than 62 years and half were younger

26.4% were diagnosed with stage 0 cancer

71.2% were diagnosed with stage I or stage II cancer

71.2% had some college education

The survey asked the women:

how much they wanted genetic testing

whether they had talked to a doctor or health professional about genetic testing

if they had met with a genetic counselor

if they had genetic testing

Overall, 66% of the women said they wanted genetic testing, but only 29% actually had genetic testing.

The researchers then split the women into two groups: those considered at high risk for a genetic mutation linked to breast cancer (773 women) and those considered at average risk (1,678 women).

Women were classified as high risk if they had one or more of the following characteristics:

diagnosed at age 45 or younger

diagnosed with cancer in both breasts

diagnosed with triple-negative breast cancer at age 60 or younger

had a relative with ovarian cancer or had a male relative diagnosed with breast cancer

two or more first-degree relatives were diagnosed with breast cancer

Ashkenazi Jewish ancestry

family history of a genetic mutation linked to breast cancer

Among women with an average risk of a genetic mutation linked to breast cancer:

59.3% wanted testing

35.9% said they talked to their doctor or another health professional about testing

14.4% met with a genetic counselor

17.8% had testing

Among women at high risk of a genetic mutation linked to breast cancer:

80.9% wanted testing

70.9% said they talked to their doctor or another health professional about testing

39.6% met with a genetic counselor

52.9% had testing

This means that about only 60% of high-risk women who had genetic testing met with a genetic counselor.

The most common reasons high-risk women gave for not having genetic testing were:

my doctor didn’t recommend it (56.1%)

too expensive (13.7%)

didn’t want it (10.7%)

my family didn’t want me to have it (0.2%)

"We found that genetic counseling and testing are not well-matched to medical need," said Allison Kurian, M.D., associate professor of medicine and of health research and policy at Stanford, who is the study’s lead author. "Women are very interested in genetic testing but many fail to receive it. This is particularly worrisome because it means that doctors are missing the opportunity to prevent cancers in mutation carriers and their family members."

"Genetic testing results can affect what sort of surgery a woman may choose to treat her existing breast cancer, as well as what treatments she should pursue to reduce the risk of forming new cancers in the future," said Reshma Jagsi, M.D., professor and deputy chair of radiation oncology at the University of Michigan and one of the study’s senior authors. "We don't have a crystal ball, but genetic testing can be a powerful tool for certain women. It is worrisome to see so many of those women at highest risk for mutations failing even to have a visit focused on genetic counseling."

"The fact that many women are not offered genetic testing after a diagnosis of breast cancer is an important illustration of the challenges of driving advances in precision medicine into the exam room," said Steven Katz, M.D., professor of medicine and of health management and policy at the University of Michigan and the study’s other senior author.

"It is likely that some doctors don't realize the benefit that genetic testing provides," Kurian added. "They may also lack the ability to explain the testing process and results clearly with patients. Priorities for the future should include strategies to expand the genetic counselor workforce and interventions to improve physicians' skills in communication and cancer risk assessment."

These results suggest that many high-risk women who should have genetic testing aren't having that screening done. This is troubling. Women with a genetic mutation linked to breast cancer have a number of options to reduce breast cancer risk and the risk of breast cancer coming back (recurrence), as well as ways to detect any cancer that develops early, when it's most treatable. These risk reduction steps include:

a more aggressive screening plan starting at an earlier age

hormonal therapy to block the effect of estrogen on breast tissue or reduce the amount of estrogen in the body

removing the healthy breasts (prophylactic mastectomy)

Some women with an abnormal BRCA1 or BRCA2 gene also may consider having healthy ovaries removed because of the increase in ovarian cancer risk. Removing the ovaries also dramatically lowers estrogen levels, and lower estrogen levels can reduce the risk of hormone-receptor-positive breast cancer.

Knowing that a woman has an abnormal BRCA1 or BRCA2 gene also is important information for the other women and men in her immediate family to have; they also may be carriers and at a higher risk of cancer.

The Gail score is a standard breast cancer risk assessment tool that assesses breast cancer risk based on a series of personal health questions that women and their doctors answer together. The questions ask about risk factors such as age, child-bearing history, family history of breast cancer, and breast biopsy results. The Gail score estimates the risk of developing invasive breast cancer in the next 5 years. If you think you may be at high risk for breast cancer, you might want to talk to your doctor about your personal and family medical history. You may want to ask your doctor to consider calculating your Gail score and then talk about what it means. You also may want to ask your doctor if genetic testing or a referral to a genetic counselor makes sense for you.